textproduct: Rapid City

KEY MESSAGES

- Marginal to Slight (Level 1-2 out of 5) risk of severe thunderstorms this afternoon and evening. The primary threat is damaging winds, but large hail may also occur.

- After cooler temperatures today, very hot weather will return Friday and continue through the weekend, with Sunday being the hottest.

- Isolated thunderstorms possible on Friday, then dry weather expected for the weekend.

UPDATE

Issued at 1030 PM MDT Wed Jul 29 2026

Water vapor imagery and KUDX radar both showing a mid-level circulation associated with a strong shortwave crossing the western SD plains and just now moving into central SD. This has been the focus for this evening's convection, which will exit to the east over the couple of hours or so. Weak elevated convection will be possible overnight into Thursday morning given rich low level moisture and moderate mid-level lapse rates...and any old intersecting outflow boundaries. Water vapor is also showing the next strong wave now crossing UT/eastern ID, which is currently supporting showers/isolated storms across the higher terrain. Ahead of the wave...ample moisture with PWATs of 150-175% of normal and moderate instability will allow for storms to develop even in the mid/late morning hours. SBCAPE up to 1800 J/kg is expected by 18z across NE WY/far western SD...and up to 3000 J/kg over SCentral SD combined with little to no CIN areawide will help get things started earlier than normal. However, shear is lacking overall which will keep storms from becoming more organized. Still, with strong instability in place and a cool front sagging southward, could see some strong to severe storms develop during the afternoon across the western SD plains...and even more so over the SCentral SD plains where low level forcing and shear is a little better. Highs will be relatively cooler tomorrow (mid to upper 80s) due to cloud cover and the aformentioned cool front.

DISCUSSION

(This Afternoon Through Tuesday) Issued at 1106 AM MDT Wed Jul 29 2026

16z surface analysis had trough from eastern MT to central CO. Water vapour loop had upper ridge from NM into eastern MT/WY with a couple of ridge-riders over southeast MT and western WY/UT. 0.5km 1-minute visible satellite loop showed most activity was elevated at this point, although there is a CU field over south- central SD associated with oppressive Td/s in the lower 70s. Effects of these features the main short term forecast concern.

This afternoon/tonight, heat indices will be in the lower 100s east of the Black Hills so hoisted a Heat Advisory earlier to account. Main shortwave rotates around upper ridge later this afternoon and evening. At least 1-2KJ/kg MLCAPE pools ahead of surface trough with 25-35kts of effective shear forecast. Bufkit soundings suggest damaging winds would be the main threat with severe convection (marginal to slight (1-2 out of 5)) risk over CWA, highest over northwestern SD. Latest CAMs/HREF emphasize this thinking. So, expect a couple clusters of severe convection this afternoon/evening moving across the CWA. If cold pools can congeal, could see a line of severe thunderstorms for a period which some CAM solutions suggest. Activity will weaken overnight, but decent low level jet likely to sustain convection. Temperatures will be near guidance.

Thursday, compact mid-level circulation moves across the CWA with continued chances for thunderstorms as a cold front slices through the area leading to "cooler" temperatures. Cold front may be focus for active/severe thunderstorms Thursday afternoon over south-central SD. Temperatures will be near guidance.

Lingering PoPs Friday given way to robust thermal ridge expansion for the weekend with Sunday highs from 100-110F putting pressure on some records. Mostly dry, but it is the northern Plains, so thunderstorms cannot be completely ruled out. Next week looks "cooler" as upper ridge flattens and west/northwest flow aloft develops, sure to provide shortwaves to create daily chances of thunderstorms. Confidence is growing for the brief cooldown.

AVIATION

(For the 12Z TAFS Through 12Z Friday Morning) Issued At 513 AM MDT Thu Jul 30 2026

Showers over NE WY nearing the Black Hills will continue E/NE this morning. More showers and thunderstorms will quickly develop late this morning into the early afternoon. MVFR/IFR will be possible near any storms, along with gusty, erratic winds even some distance from the storms. Storms will end from west to east through the afternoon and evening hours. A cold front crossing the area today will bring breezy northerly winds through the afternoon.

FIRE WEATHER

Issued At 1106 AM MDT Wed Jul 29 2026

Elevated fire weather conditions are expected this week due to hot temperatures as well as minimum relative humidity in the teens and 20s. Hotter weather develops for the weekend with even drier air (MinRH as low as 8%), so critical fire weather conditions are likely. Thunderstorm chances highest this afternoon through Friday and then early next week. The cores of thunderstorms that occur through Friday should contain wetting rain, but lightning strikes outside of the cores as well as strong, erratic winds may create opportunities for new fires.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.